The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 2001-213497, filed Jul. 13, 2001, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an ignition device for a personal watercraft engine.
2. Description of Background Art
Small two-cycle engines are commonly used for personal watercraft. Typically, the ignition is disposed in a sufficient space above a cylinder head of the engine. In prior art devices, ignition current is supplied via a high-tension cord from an ignition coil disposed on a side of the watercraft body to a spark plug in a cylinder head of the engine. However, since high-tension current flows from the ignition coil to the spark plug, if water droplets adhere on a surface in the vicinity of either, current leakage may occur, and current may escape via the water droplets. Accordingly, special measures are required to prevent current leakage, for example, waterproofing high-voltage areas and arranging and waterproofing the ignition coil.
In recent years, there has been a growing demand for four-cycle personal watercraft engines to reduce environmental damage caused by exhaust gas and noise pollution. However, a disadvantage associated with four-cycle personal watercraft engines is that a four-cycle engine is substantially higher than its two-cycle counterpart with the same displacement. As a result, if a four-cycle engine is mounted in the narrow body of a personal watercraft, much less space is available above the engine than if a two-cycle engine is mounted. Clearly, it is difficult to lay a high-tension cord and the like in such a cramped space.
It is an object of the present invention is to provide an ignition device for a personal watercraft engine which allows for the mounting of a four-cycle engine and which prevents current leakage.
To achieve these objects, a personal watercraft engine ignition device is provided which includes an engine for driving a jet propelling pump disposed in the watercraft body, which body is surrounded by a hull and deck. A spark plug for spark ignition is located in a cylinder head of the engine. An ignition coil having an integral cap is provided on the spark plug, and is mounted in a watertight manner on the cylinder head, thus constituting a waterproof structure.
In one embodiment, the ignition coil is disposed on an uppermost portion of the engine at a position higher than an open opening of an intake duct for supplying air to the watercraft body.
Also included are a female case connector portion provided on the cap of the integral cap ignition coil and a recess for receiving the cap and a water-escape groove continuous to the recess formed in a upper surface of the cylinder head. The escape groove is formed so as to extend from the recess to an opening of the female case connector portion. A bottom surface of the escape groove is tilted downwardly from the recess to the opening of the female case connector portion of the cap.
As described above, the engine for driving the jet propelling pump is provided in the watercraft body surrounded by the hull and the deck, the spark plug for spark ignition is disposed in the engine cylinder head, and the integral cap ignition coil is located on the spark plug. As a result, no high voltage portion is exposed in the watercraft body.
Accordingly, even if the inside of the watercraft body gets wet, current leakage will not occur. Thus, it is possible to prevent misfiring due to current leakage and, hence, to prevent increased hydrocarbon emissions. Further, since it is not necessary to lay a high-tension cord in a space over the engine, it is possible to mount a four-cycle engine in the narrow body of a personal watercraft.
Because the integral cap ignition coil is watertightly mounted in the cylinder head, water does not enter the area around the spark plug. This makes it possible to prevent engine misfiring due to soaking by water.
In addition, the integral cap ignition coil has a waterproof structure. As a result, it is possible to prevent water from soaking the ignition coil. By keeping out water out, engine misfiring can be prevented.
Since the integral cap ignition coil is provided on an uppermost portion of the engine and located at the remotest position from the water, even if water enters the watercraft body, it is possible to more positively prevent engine misfiring due to leakage of current.
Further, the intake duct for supplying intake air in the watercraft body is provided in the watercraft body and the integral cap ignition coil is provided at a position higher than that of the opening of the intake duct formed in the watercraft body. As a result, less of the water which may be splashed into the watercraft body via the intake duct reaches the ignition coil, again preventing engine misfire due to current leakage.
As described earlier, the female case connector portion is provided on the cap of the integral cap ignition coil, the recess for receiving the cap and the water-escape groove continuous to the recess are formed in an upper surface of the cylinder head, and the escape groove is formed so as to extend from the recess to an opening of the female case connector portion. Further, a bottom surface of the escape groove is tilted downwardly from the recess to the opening of the female case connector portion of the cap. As a result of this configuration, even if water splashes around the integral cap ignition coil onto the upper portion of the engine, the water can be readily discharged via the escape groove.
Since the escape groove tilts downwardly from the recess to the opening of the female case connector portion of the cap, when water is discharged, the water is not directed toward the opening of the connector portion. This feature further contributes to preventing engine misfire due to current leakage.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.